ezyZip is a free service that zip or unzip files online without having to use desktop applications like Winzip or Winrar. There is no mention as to how many files you can unzip so I guess it’s safe to assume that you can work with unlimited number of files. The more files you work with the longer the process will be, though. However, you can only zip one file at a time.
Best of all, ezyZip doesn’t require the files to be uploaded, but you must have installed Java for this. ezyZip doesn’t require any registration at all, too. Go to the site and use it instantly.